Turbine driven fuze



TURBHNE DRIVEN FUZE Ralph N. Harmon and Edward J. Naumann, Baltimore, Md., assignors, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application June 4, 1945, Serial No. 597,572 1 Claim. (Cl. 1Q281.2)

This invention relates generally to ordnance fuzes and more particularly to an improved type of mechanical power supply for operating the various control elements of such fuzes.

In certain of its aspects this invention is related to a copending application of R. N. Harmon and E. J. Naumann, Serial No. 597,573, filed on the same date as this application, now Pat. No. 2,687,482, entitled Electrically Operated Devices, and assigned to the same assignee as this invention.

Fuzes of the type used in the past were usually equipped with a propeller mounted at the forward extremity thereof. This propeller drove an arming mechanism which in the case of a contact type of fuze operated a barrier of some sort to a position in which it no longer obstructed the path of movement of a plunger or firing pin which set 01f the detonator and which, in the case of the proximity type of fuze, sometimes operated arming contacts to complete the necessary circuits through which the detonator was fired.

Externally mounted propellers were not satisfactory for a number of reasons. Such propellers were usually made of fairly heavy sheet metal and were mounted directly at the front of the fuze which, when installed, placed the propeller directly at the front end of the projectile. When a projectile so equipped was projected into the atmosphere, the propeller blades quite frequently, because of the high air pressure, were bent back against the projectile casing or fuze head depending upon the design and so prevented from rotating. As a consequence the projectile which depended upon propeller rotation for arming did not arm and proceeded to its objective as a dud. To increase the size of the propeller as far as its cross-sectional dimensions are concerned to make it stronger offered no practical solution to the problem, since it usually resulted in a longer fuze, a matter which could not be tolerated. An example which demonstrates how critical fuze dimensions are is had in the case of fuze equipped bombs. The bomb weight which a plane may carry is not always limited by the aerodynamic power developed but often by the available space for carrying a cargo of given dimensions. Bomb dimensions for given weights have, in the past, been standardized to a considerable extent and bomb racks on aircraft designed accordingly. With the advent of safety propeller driven arming and control devices for bombs, bomb lengths for a given weight of bomb increased to such an extent that in many cases an aircraft might accommodate in its bomb racks only about half or less of its normal weight of bombs. In other words, the fuze length is a critical consideration.

Further, with the external propeller driven fuze, the propeller had to be detached from the fuze for shipping purposes to prevent propeller damage and also to conserve space. Thus it was necessary to attach the propeller to the fuze when the fuze was to be used. This operation was not only time consuming but more importantly was a delicate operation involving some danger to personnel as well as equipment.

A principal object of this invention is to provide an ordnance fuze which is simple in its elements and effective in its operation.

Another object of this invention is to provide an ordnance fuze of minimum size and otherwise of such configuration as to permit the fuze equipped projectile to be handled in standard apparatus, as well as not to interfere to an appreciable extent, if not at all, with the flight of the projectile.

Another object of this invention is to provide an improved mechanical power system for an ordnance fuze.

Another object of this invention is to provide a fluid operated device for an ordnance fuze adaptable for use in small spaces.

A specific object of this invention is to provide a fluid operated drive for the control elements of an ordnance fuze which is located internally of the fuse.

Another specific object of this invention is to provide a drive for the control elements of an ordnance fuze which may be permanently assembled as a part of the fuze and does not require disassembly for shipping purposes.

Other objects and advantages will become apparent upon a study of the following specification when considered in conjunction with the accompanying drawings, in which:

Figure l is a sectional view of a proximity fuze embodying the principles of this invention;

Fig. 2 is a modification of the invention illustrated in Figure 1;

Fig. 3 is a view looking into the front of the turbine of Fig. l with the front section of the fuze housing removed;

Fig. 4 is a sectional view taken on the line IVIV of Figure 1;

Fig. 5 is a sectional view taken on the line V-V of Fig. 2;

Fig. 6 is a sectional view taken on the line VIVI of Fig. 2; and

Fig. 7 is a block diagram of the electrical components of a Doppler operated system.

Referring now to the drawings there is illustrated in Figure 1 an electrical proximity fuze of the Doppler operated type. Such a fuze depends for its operation upon the amplitude of a beat signal developed as a consequence of suitable mixing of a transmitted and reflected signal.

This involves suitable electronic equipment of a typical type illustrated in Fig. 7 including a radiating heterodyne detector, a shaped amplifier for the detector output circuit, a trigger circuit including, for example, a thyratron tube triggered by the amplifier output and which energizes a heater adapted for igniting a squib forming part of a powder train which detonates the projectile.

The radiating heterodyne detector applies a signal to.

the antennae which is then transmitted to the projectiles objective. This signal is reflected at the objective and picked up in the fuze circuits. The reflected signal in most cases is of a higher frequency than the transmitted or direct signal because of the relative motion between the projectile and target. Consequently, upon mixing of the direct signal and received signal, as in a heterodyne receiver, a beat signal is produced. This beat signal passes through the amplifier and is used to control the grid of a thyratron tube in the trigger circuit. When the beat signal is of sufficient amplitude it causes the thyratron to become conducting after which detonation of ,the projectile, as previously explained, occurs. plied to the fuze system by the generator G which is driven by the fluid operated device attached to the permanent magnet rotor thereto.

or antennae 2 to which the radiating heterodyne detector Patented June 11, 1957 Power is supis connected. The dipoles or antennae 2 are shown only fragmentarily since their proportions are unessential to this invention. The fuze body consists of a metal diecasting 3 of non-magnetic material, for example, man- 1ganese,provided with a cylindrical externallythreaded section 4 which threads into the nose of the projectile 5. A small generator (not shown) is housed within the section 4 and has a perm anent magnet rotor journalled in bearings in this housing section. The shaft of this generator extends into the turbine chamber formed in the enlarged end of the die-casting 3. The forward extremity 1 of the fuze, which carries the dipoles and houses the electronic elements of the radio transmitting and receiving system, is preferably formed of a high strength plastic having good electrical insulating properties. It is formed in two main sections, one of which is a plate integral therewith. Gear 37 drives the large output gear 38 having the shaft 39 secured to rotate therewith. Shaft 39 extends into the arming contact chamber and in this chamber is slotted along a portion of its length to receive a complementary projection of the externally threaded member 40 which is thus secured to the reduction gear unit output shaft. A disc 41 comprising a central metallic threaded section which threads onto the threaded memher 40, and an outer insulating section, is provided with projections 42 on the periphery thereof, which operate in slots '43 in the arming contact chamber, to prevent the disc from following rotational movements of the threaded member 46. Spring contacts 44 are secured to the arming 1 contact housing and mating contacts 45 are carried in like member 8 having an aperture 9 centrally thereof and i the other section 10 being provided with a plurality of recesses (not shown) internally thereof for receiving certain electrical circuit elements. In addition an aperture 11 is provided centrally of the section 10. A circumferential groove in the plate like member or housing section 8 receives a complementary edge of the housing section 10, in which assembled relation of the housing sections the apertures 9 and 11 are coaxially disposed. A tubular section 12, as shown, is fabricated as a part of the chassis 13 of the radio units, joins the apertures thereby forming the passage 14 through the assembled housings, which passage at its frontal extremity is completed by a plate 15 which seals the front of the housing section 10 and presents a smooth curved surface to the air stream entering the passage 14 upon motion of the fuze through the atmosphere. A plug terminal 17 of insulating material completes the lower portion of the turbine chamber. All wires leading from the generator and to other electrical elements of the fuze, such as the heater for igniting the squib (not shown) pass through this plug. A complementary receptable (not shown) in the plate 8 carries these circuits through to the electronic elements in the housing section 10. This assembly of housing sections is secured by means of through bolts 18 which pass through the housing sections 10 and 8 and thread into the housing section 3. A pair of radially disposed passages 19 (see also Fig. 3) in the housing section-3, provide exhaust exits for the turbine chamber from which they extend. The end of the generator shaft which extends into the turbine chamber is screw threaded to receive the hub of the turbine rotor 28'which thereafter is locked in threaded position by means of the lock nut 29.

The drawing illustrates a form of turbine which has been found very satisfactory in practice. It is simple to construct and possess ample structural strength to ,withstand the high speeds at which it is aerodynamically suited for operation. It is made of a simple disc punching 59 from sheet plate material. The blades 58 are cut along three sides from the disc punching and then bent rearwardly from the disc surface abouttherernaining uncut side as the hinge, the angle andarea of the blades depending upon a number of considerationsamongwhich the velocity and volume transfer'o'f'the air stream as well as the desired operating speed are important. It is not to be construed, however, that the invention is limited to this specific blade construction. There are numerous other turbine designs which may be substituted for that illustrated without departing from the principles of this invention. V I

The other extremity of the generator shaft which extends into the gear reduction unit31 is turned to the shape of a worm 32 which meshes with theworm wheel 33. The other end of this worm wheel shaft is also worm cut, but which cannot be seen in the drawing, to mesh with a worm wheel 34. Worm wheel 34 drives the small gear 35 secured to rotate therewith, which, in

turn, drives the large gear 36 having the small gear 3'1 the insulating portion of the disc 41. The disc moves to the left, as viewed in Figure 1, when the threaded member 40 rotates and the contacts close. Thereafter the disc 41 runs off the threads of the threaded member where it is locked incontacting position by the thread extremities without interfering with further rotational movements of the threaded member. Thus the turbine drive through the generator and gear reduction unit is unimpeded.

When the projectile is in free flight an air stream is induced through the turbine chamber, which is the result of the pressure differential existing between the em trance and exhaust passages of the turbine. chamber. The air stream flows through the passage 14 which is directed 'into'the relative wind and then flows radially in the turbine chamber through the holes in the turbine disc where it impinges on the turbine blades and drives the turbine around in rotation. As the turbine increases in speed the generator output increases and, through the electrical connections before noted, energizes the electronic system,

causing the tubes thereof to be heated and after a short interval a signal is applied along the dipoles. After a short time interval sufiicient to permit safe arming, the turbine will have made the required number of revolutions to'drive the contact disc 41 to a position in which the arming contacts 44 and 45 areclosed. When the beat signal reaches a predetermined amplitude indicating the projectile is in preset proximity of its objective the thyratron tube is triggered by the amplifier output and discharges through the arming contacts 44 and 45 into the heater, igniting the squib and associated powder train (not shown) which detonates the projectile.

In order to obviate unwanted rotation of the turbine rotor,'a suitable safety device generally designated 46 is provided to prevent the rotor from continuously rotating,'for' example, during shipping and While the bomb is being carried to its objective. To this end a plunger 47, located in the fuze housing section 3 and having a rod 48 extending into the path traversed by the turbine blade tips, is provided to limit angular or'rotative movements of the rotor'between limits imposed by the circumferential spacing of any two of the blades. This plunger is biased away from its turbine blade engaging position ..by-a compression spring 49, and maintained in its blade engaging position as shown, by means of the safety wire 5:) inserted through suitable holes 51 in the Walls of the cylinder 52 ;in which the plunger operates. With this arrangement, the fuze may be manufactured as a completely assembled unit and so shipped without'any danger of the fuze becoming armed as a result of rotationa1 freedom of the turbine rotor. By way of specific example, when a fuze equipped bomb is loaded in the bomb racks of an aircraft, one extremity of an arming wire, the other extremity of which is releasably attached at some suitable point on the airframe, is inserted through the holes 51 and thereafter the safety wire Stlmay be removed. When thebomb releasing mechanismis actuated and the bombs drop away from the aircraft, the arming wire is jerked from the holes 51, the compression spring I ejects the plunger "and the turbine blades are rotated by the air stream passing through the turbine passages.

The application of the turbine hereinbefore set forth to a contact type of fuze is indicated in Figs. 2, 5 and 6. Like the proximity fuze, this contact fuze is provided with an opening in the forward or leading extremity of the fuze but which in this case forms an opening to a relatively shallow longitudinal recess of cylindrical plan form as seen in Fig. 5. A suitable number of radially disposed exhaust openings 19a are provided near the inner end of the longitudinal passage or recess. A hollow shaft 53 is journalled in bearings 54 which seat in the fuze body. This hollow shaft is threaded at the extremity projecting into the turbine chamber to receive the hub 55 of the turbine rotor and the locking nut 55a. A firing pin 56 slides in the hollow shaft 53 and is biased to the left, as viewed in Fig. 2, by the compression spring 57. The rotor blades 58 like those of the turbine of Figure 1 are punched from a circular disc 59 having an outside diameter just slightly smaller than the diameter of the circular passage in which it rotates and provided with a hole in the center which encircles a mating surface on the rotor hub to concentrically locate the turbine disc on the hub 55. Thereafter the hub and disc assembly is suitably securely joined. As indicated, the disposition of the rotor in the circular passageway is such that the disc, for the most part, forms a barrier between the open end of the circular passageway and the exhaust openings. Thus upon a pressure unbalance between the circular opening at the leading edge of the fuze body and the exhaust openings as occurs during relative movement of the fuze body and the surrounding fluid medium, the major portion of the resulting air stream must flow through the disc openings and impinge upon the rotor blades. The forces resulting from the action of the air stream on the inclined surfaces of the rotor blades produces a torque which causes rotation of the turbine rotor.

Rotative movements of the rotor tends in some measure to cause rotation of the air behind the rotor in the direction of rotation of the rotor. The centrifugal reaction of the rotating air mass thus results in a force which tends in some measure to additionally accelerate the air stream in the direction of the exhaust openings.

The tubular turbine rotor shaft is cut in the form of a pinion 61 at the end opposite the turbine which projects into the reduction gear unit 62. Pinion 61 drives gear 63 having small gear 64 fixed for rotation therewith. Small gear 64 meshes with large gear 65 having a small gear 66 secured thereto. Small gear 66 drives the large output gear 67 which extends through the gear housing into the arming mechanism chamber and at its extremities in that housing carries a worm 68 (see Fig. 6). Worm 68 drives worm wheel 69, the shaft 70 of which is journalled in supports punched from plate 71 of the gear unit. This shaft is threaded along a portion of its length. Block 72 which operates between the plate 71 and end closure 73 threadedly engages the threaded portions of shaft 70. It is normally disposed to block movement of the firing pin 56 through the hole 74 in the end closure 73. When the turbine drives the gear unit, block 72 is threaded downwardly as viewed in Figs. 2 and 6 and thus moves from the path of the firing pin. As shown the block runs off the threads of shaft 70 to permit free rotation of the turbine drive. This is not an essential feature, however, unless other arming features are to be controlled by further rotation of the turbine.

When the fuze equipped projectile srtikes its objective, the firing pin is driven through the opening 74 into the fuze section 75 to strike a cap (not shown) forming part of a powder train in the section 75 which is utilized to explode the main powder charge of the projectile.

In this embodiment of the invention like that illustrated in the preceding figures of the drawing, a safety device 46 is provided to obviate unwanted rotative movements of the rotor thereby preventing premature arming of the fuze. The rod 48 of the plunger 47 again protrudes into the path traversed by the rotor blades to limit (angular movement of the turbine rotor depending upon the circumferential spacing of any two of the rotor blades. With a safety device of the character disclosed, the turbine does not operate until the arming wire is removed. As before described, this wire is not removed until the fuze equipped projectile is ready for use and an arming wire substituted therefore.

The foregoing disclosure and the showings made in the drawings are merely illustrative of the principles of this invention and are not to be considered in a limiting sense. The only limitations are to be determined from the scope of the appended claim.

We claim as our invention:

An ordnance fuze comprising, in combination, a housing section of substantially circular form having a reduced diameter portion externally threaded for threaded engagement in the nose of a projectile, said housing section having a pair of arcuate sections projecting from the forward fiace thereof in diametrically disposed relation, a turbine rotor having a plurality of radially disposed blades arranged with the inner radial extremitiesv thereof in a circle of predetermined diameter, means journalling said rotor in said housing section for rotation between said arcuate sections, a second housing section of configuration conforming to the substantially circular form of the first mentioned housing section and having an opening centrally thereof of smaller diameter than the circle defined by the inner radial extremities of said blades, means securing the second housing section to the first mentioned housing section against said arcuate sections forming an enclosure for said turbine rotor in which the exhaust passages are defined between said arcuate sections and the inlet passage to said enclosure is formed by the opening centrally of said second housing section, arming mechanism for said fuze, and means connecting said turbine rotor to drive said arming mechanism.

References Cited in the file of this patent UNITED STATES PATENTS 532,232 DeLaval Jan. 8, 1895 637,818 Nilsson Nov. 28, 1899 676,139 Klumak June 11, 1901 1,000,862 Voller Aug. 15, 1911 1,311,785 Wildrick July 29, 1919 1,793,567 Teit-scheid Feb. 24, 1931 2,076,602 Towner Apr. 13, 1937 2,101,082 Mathsen Dec. 7, 1937 FOREIGN PATENTS 1,089 Great Britain of 1912 304,254 Germany Oct. 1, 1920 252,837 Italy Apr. 18, 1927 

